The anion channel SLAH3 regulates flowering time in Arabidopsis thaliana.

Flowering is a critical developmental event for plants. Here, we identify that the nitrate efflux channel SLOW ANION CHANNEL HOMOLOG 3 (SLAH3) regulates flowering time in Arabidopsis thaliana. The slah3-4 mutant exhibited early flowering and reduced rosette leaf number under both long-day and short-day conditions, while SLAH3 overexpression plants exhibited delayed flowering. This regulatory role of SLAH3 was independent of nitrate supply, as the early-flowering phenotype persisted across a range of KNO3 concentrations in hydroponic culture. Molecular analyses revealed that the expression of the floral repressor FLOWERING LOCUS C (FLC) was downregulated, whereas floral promoters including CONSTANS (CO), FLOWERING LOCUS T (FT), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and LEAFY (LFY) were upregulated in slah3-4. SLAH3 exhibited rhythmic oscillatory expression, and the circadian clock gene TIMING OF CAB EXPRESSION 1 (TOC1) exhibited altered expression in the mutant, while CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) remained unchanged. RNA situ hybridization further confirmed that SLAH3 modulates flowering time through regulating LFY expression. In summary, our results demonstrate that SLAH3 plays an important biological role in regulating floral transition in Arabidopsis.